【International Papers】Plasma-free anisotropic selective-area etching of β-Ga₂O₃ using forming gas under atmospheric pressure

      Researchers from the National Institute for Materials Science have published a dissertation titled "Plasma-free anisotropic selective-area etching of β-Ga₂O₃ using forming gas under atmospheric pressure" in Science and Technology of Advanced Materials.

ABSTRACT

      We demonstrate a facile and safe anisotropic gas etching technique for β-Ga₂O₃ under atmospheric pressure using forming gas, a H₂/N₂ gas mixture containing 3.96 vol% H₂. This etching gas, being neither explosive nor toxic, can be safely exhausted into the atmosphere, simplifying the etching system setup. Thermodynamic calculations confirm the viability of gas-phase etching above 676°C without the formation of Ga droplets. Experimental verification was achieved by etching¯ (102) β-Ga₂O₃ substrates within a temperature range of 700–950°C. Moreover, selective-area etching using this method yielded trenches and fins with vertical and flat sidewalls, defined by (100) facets with the lowest surface energy density, demonstrating significant anisotropic etching capability.

Figure 1. Equilibrium partial pressures of gaseous species above β-Ga₂O₃ in (a) N₂-diluted H₂ gas flow with 4.0 vol% H₂ and (b) undiluted H₂ gas flow under 1 atm as functions of temperature. Red solid lines represent the partial pressures of gaseous species, while the vapor pressure of pure Ga metal (P^v_Ga) is shown with blue dashed lines. The green dotted line T_X indicates the temperature at which the partial pressure of Ga (P_Ga) equals  .

Figure 2. Schematic of the forming-gas etching system utilized in this research.

DOI：

doi.org/10.1080/14686996.2024.2378683